This invention relates to a pump jack drive apparatus, and in particular to an apparatus for driving and controlling the speed of operation of a pump jack.
There are presently available a number of alternative forms of pump for pumping oil. Because of their unreliability and expense, such pumps have not replaced the conventional pump jack in oilfields. The pumping of heavy oils presents certain problems. If such problems can be overcome, the production of heavy oils can be substantially increased.
The motion of the walking beam of a conventional pump jack is derived from a rotating eccentric. The stroke cycle is normally fixed and resembles a sine wave. In order to pump efficiently, the pumping cycle cannot be changed. When pumping heavy oil, the pumping cycle may be altered which is one of the problems referred to above. In the production of heavy oils, it is advantageous (1) to be able to change the rate of pumping and stroking profile, or (2) to be able to maintain the rate of pumping constant at a predetermined level.
Because of the relatively low production rates of heavy oil, the equipment used to control pumping with a pump jack should be inexpensive and reliable. The object of the present invention is to meet such demands by providing a relatively simple, inexpensive apparatus for driving and controlling operation of a pump jack.